1. Field of the Invention
In one of its aspects, the present invention relates to an ultraviolet radiation lamp. In another of its aspects, the present invention relates to a radiation source module comprising the ultraviolet radiation lamp. In another of its aspects, the present invention relates to a fluid treatment system comprising the ultraviolet lamp.
2. Description of the Prior Art
Fluid treatment systems are known generally in the art.
For example, U.S. Pat. Nos. 4,482,809, 4,872,980, 5,006,244, 5,418,370, 5,504,335, 5,539,210 and 5,590,390 (all in the name of Maarschalkerweerd and all assigned to the assignee of the present invention), the contents of each of which are hereby incorporated by reference, all describe gravity fed fluid treatment systems which employ ultraviolet (UV) radiation.
Generally, such prior fluid treatment systems employ an ultraviolet radiation lamp to emit radiation of a particular wavelength or range of wavelengths (usually between 185 and 400 run) to effect bacterial kill in or other treatment of the fluid being treated. Many conventional ultraviolet radiation lamps are known as "low pressure" mercury lamps.
In use, it is usually necessary that a "cold spot" be maintained in such lamps to allow the excess mercury in the lamp to condense thereby maintaining an adequate mercury vapour pressure for efficient emission of ultraviolet radiation. If the "cold spot" temperature is not within a narrow temperature range, the mercury vapour pressure in the low pressure lamp may not be suitable for efficient generation of UV radiation. Specifically, too high or too low a "cold spot" temperature will result in loss of efficiency of emission of UV radiation. This can lead to inadequate treatment of the fluid being treated.
When such mercury lamps are used in a fluid treatment system such as one of the specific systems described and illustrated in the Maarschalkerweerd patents referred to above, the necessary "cold spot" is through heat exchange with the water being treated since the water is moving and is typically at ambient temperature. However, when it is desirable to treat a fluid such as ambient air (e.g., containing pollutants that could be photocatalyzed) or relatively warm fluids (e.g., at temperatures greater than about 40.degree. C.), there is a significant risk that the a "cold spot" having the desired suitable temperature will not be formed leading to the problems set out above.
Accordingly, it would be desirable to have an ultraviolet radiation lamp which, in use, provides the needed "cold spot" in a controllable fashion and could be used to treat ambient air, ambient gas or relatively warm fluids. It would be advantageous if the solution to the problem could be achieved with little or no redesign df the ultraviolet radiation lamp.